1. Field of the Invention
The present invention relates to light-transmitting members, and more particularly, to light transmitting members formed of optically transparent materials, for example, glass, quartz, or transparent resins etc., such as acrylic and polycarbonate (PC), and to light-transmitting members featuring a surface structure that can inhibit specular reflection at the surface while maintaining the transparency of a transparent plate, for example, a glass plate.
2. Description of the Related Art
To eliminate the annoyance or reduce the drop in visibility caused by light reflected at the surface of an object etc. getting into the viewer's visual field, in various fields, antiglare treatment is performed for suppressing glare at the object's surface by diffusely reflecting the light incident on the object's surface.
Examples of articles that are subjected to this kind of antiglare treatment include television screens, displays screens of computers, and liquid crystal displays built into various kinds of portable electronic equipment as monitors, such as digital cameras, digital video cameras, mobile telephones, car navigation systems, and so forth.
In these kinds of liquid crystal displays, indoor lighting, sunlight, etc. producing glare at the surface thereof causes a considerable drop in visibility. In particular, with the liquid crystal displays built into portable electronic equipment used outdoors, in order to maintain visibility under highly bright light such as sunlight, it is necessary to use a high-brightness backlight, which results in heavy battery consumption.
Therefore, in order to prevent such glare and maintain image visibility, the main approach is to use so-called semitransparent display devices in the case of liquid crystal displays.
These semitransparent display devices have an antireflection film, which is made translucent, for example, by forming minute indentations and protrusions on the surface of a transparent film, attached to the surface of glass substrates holding liquid crystal therebetween or to the inner side of the glass substrates, and prevent glare at the screen by diffusely reflecting incident light with minute indentations and protrusions formed on the surface of the antireflection film.
To control the reflection direction of the light without using this kind of antireflection film, a light-transmitting optical component has been proposed, which is an optical component formed of transparent resin to allow transmission of light and which has nanometer-order indentations and protrusions in at least one surface of the light-incident surfaces thereof (see claim 1 of Japanese Unexamined Patent Application, Publication No. 2009-204706).
Even in a liquid crystal display subjected to the antiglare treatment described above, if the minute indentations and protrusions formed in the antireflection film etc. are formed regularly, with a light source exhibiting parallelism, such as sunlight, rainbow-like interference colors appear at the surface to due to the interference phenomenon at the indentations and protrusions. The generation of these interference colors causes a decrease in visibility.
Methods that have been proposed as countermeasures against this interference phenomenon include making the hubbly surface profile formed on the reflecting surface of the antireflection film etc. or the surface profile of the antireflection film itself random, diffusing the interference light into irregular light with a diffuser disposed in front of the reflecting surface, and so forth.
To bring about antiglare properties by attaching an antireflection film having minute indentations and protrusions etc. in the surface thereof to the surface of a transparent plate formed of glass, quartz, acrylic, polycarbonate or the like, or by causing diffuse reflection by forming minute indentations and protrusions directly on the surface of the transparent plate, the diffuse reflection caused by the indentations and protrusions formed in the surface of the antireflection film not only reduces the specular reflection of lighting or sunlight but also causes diffuse reflection of the light passing through the transparent plate. Therefore, when this structure is employed in liquid crystal displays and so forth, the outline of the displayed image becomes blurred, and the quality of the image that can be displayed by the display device is decreased.
In addition, when the formation of the indentations and protrusions for causing diffuse reflection is achieved by attaching an antireflection film having minute indentations and protrusions formed therein to the surface as described above, it is necessary to attach the antireflection film to the transparent plate so as not to trap any air between them. Not only is this task complicated, but also in some cases the image becomes even more blurred because of a refractive index difference due to the different materials of the antireflection film and the transparent plate, which causes a further reduction in the quality of the image that can be displayed by the display device.
The present invention has been conceived to eliminate the problems with the related art described above, and an object thereof is to provide a surface structure of a light-transmitting member that can display a transmission image with a sharp outline while exhibiting high antiglare properties, and that can thus maintain the sharpness of the transmission image.